dnl as-ac-expand.m4 0.2.0
dnl autostars m4 macro for expanding directories using configure's prefix
dnl thomas@apestaart.org
dnl
 
dnl AS_AC_EXPAND(VAR, CONFIGURE_VAR)
dnl example
dnl AS_AC_EXPAND(SYSCONFDIR, $sysconfdir)
dnl will set SYSCONFDIR to /usr/local/etc if prefix=/usr/local
 
AC_DEFUN([AS_AC_EXPAND],
[
    EXP_VAR=[$1]
    FROM_VAR=[$2]
 
    dnl first expand prefix and exec_prefix if necessary
    prefix_save=$prefix
    exec_prefix_save=$exec_prefix
 
    dnl if no prefix given, then use /usr/local, the default prefix
    if test "x$prefix" = "xNONE"; then
        prefix="$ac_default_prefix"
    fi
    dnl if no exec_prefix given, then use prefix
    if test "x$exec_prefix" = "xNONE"; then
        exec_prefix=$prefix
    fi
 
    full_var="$FROM_VAR"
    dnl loop until it doesn't change anymore
    while true; do
        new_full_var="`eval echo $full_var`"
        if test "x$new_full_var" = "x$full_var"; then break; fi
        full_var=$new_full_var
    done
 
    dnl clean up
    full_var=$new_full_var
    AC_SUBST([$1], "$full_var")
 
    dnl restore prefix and exec_prefix
    prefix=$prefix_save
    exec_prefix=$exec_prefix_save
])
